Metal powder ignition apparatus, metal powder ignition method, compact metal powder combustion apparatus and metal powder combustion method using water plasma

ABSTRACT

A metal powder ignition apparatus using water plasma is provided. The metal powder ignition apparatus includes an ignition apparatus for igniting and combusting metal powder by injecting the water plasma into a mixture of the metal powder and steam functioning as an oxidizer for burning the metal powder.

CROSS REFERENCE TO RELATED APPLICATION

This application claims the benefit under 35 U.S.C. 119(a) of Korean Patent Application No. 10-2011-0091362, filed on Sep. 8, 2011, the disclosure of which is incorporated by reference in its entirety for all purposes.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a metal powder ignition apparatus, a metal powder ignition method, a compact metal powder combustion apparatus, and a metal powder combustion method using water plasma.

2. Description of the Related Art

A variety of clean energies such as solar energy, wind power, tidal power and the like are emerging as an alternative energy to cope with limited reserves of hydrocarbon (CxHy) fuel and environmental pollution. Among them, metals are attempted to be actively used as an energy source capable of generating large amount of energy in a short time period.

For example, among the metal materials, aluminum is abundantly reserved as much as to be about 8.2% of the mass of elements existing in the earth, and it can be easily purified thanks to the progress in the techniques of processing thereof. In addition, alumina (Al₂O₃) generated by burning the aluminum is renewable through reprocessing, and hydrogen generated in the combustion process can be used as an energy source of a fuel cell.

FIG. 1 shows reaction formulas and reaction heats of hydrocarbon (C₃H₈) fuel, aluminum, and magnesium, and FIGS. 2 and 3 show a process of igniting aluminum metal particles.

Referring to FIG. 1, it is confirmed that reaction between the aluminum and water generates much more energy than the hydrocarbon fuel does. Using this characteristic, the aluminum can be conveniently used in the field of explosives, space and seawater propulsion systems and the like which require high energy.

Although such a metal is abundantly reserved and environmentally and economically advantageous compared with hydrocarbon fuels, it is not generally spotlighted as an alternative clean energy. It is since that its ignition mechanism is complex and ignition itself is difficult due to an oxide film having a high melting point of 2,345K, as shown in FIGS. 2 and 3.

Previously, examples of using hydrogen-oxygen flame as a source of ignition and oversupplying 700K steam as an oxidizer more than 20%, or examples of using a fluidized bed powder fuel feeding system with a piston are introduced as an effort to reduce ignition delay time.

However, conventionally, they are merely at an experimental level of confirming possibility as a propulsion system or an energy generation system using metal powder by implementing only ignition and combustion of the metal powder and analyzing dynamic combustion characteristics of the metal powder. Therefore, it needs to develop a metal powder combustor capable of practically using a metal fuel as an important energy source so as to be generally used in industry.

SUMMARY OF THE INVENTION

Therefore, the present invention has been made in view of the above problems, and it is an object of the present invention to provide a metal powder ignition apparatus, a metal powder ignition method, a compact metal powder combustion apparatus, and a metal powder combustion method using water plasma, appropriate for implementing a metal powder combustor which allows a metal fuel to be stably used as an environment-friendly alternative energy source.

To accomplish the above object, according to one aspect of the present invention, there is provided a metal powder ignition apparatus using water plasma, which ignites and burns metal powder by injecting the water plasma into a mixture of the metal powder and steam functioning as an oxidizer for burning the metal powder.

Here, the metal powder may be manufactured using aluminum or magnesium, and the water plasma may be high-temperature plasma of 1,000° C. or higher generated by ionizing the steam.

In addition, according to another aspect of the present invention, there is provided a metal powder ignition method using water plasma, the method for igniting metal powder in a combustion chamber 300 using the water plasma while feeding only a right amount of the metal powder and the steam into the combustion chamber 300.

Here, the metal powder and the steam may stay inside a space unit of a limited length in the combustion chamber 300 for a further extended period of time and proceed toward one side by swirl flow, and the water plasma may be injected toward the center of the combustion chamber 300 positioned at the core of the swirl flow, in the proceeding direction of the metal powder and the steam.

In addition, according to another aspect of the present invention, there is provided a compact metal powder combustion apparatus using water plasma, the apparatus comprising: a combustion chamber 300; a metal powder feeder 100 for feeding the metal powder into the combustion chamber 300; a steam feeder 200 for generating steam of 200 to 400° C. and feeding the steam into the combustion chamber 300; and a water plasma igniter 400 for igniting the metal powder and the steam fed into the combustion chamber 300, using the water plasma.

Here, the combustion chamber 300 may include: a tangential feed tube 310 having a feed terminal connected to an outer circumference of the combustion chamber 300 in a tangential direction, for generating swirl flow by feeding the metal powder and/or the steam into the combustion chamber 300 in the tangential direction.

In addition, the combustion chamber 300 may include: a turbulence chamber 320 having feed terminals of a first tangential feed tube 311 for feeding the metal powder and a second tangential feed tube 312 for feeding the water, arranged on the outer circumference at predetermined intervals, and forming a narrow disk-shaped mixing space unit in which the metal powder and the steam fed through the first and second tangential feed tubes 311 and 312 are mixed while swirl-flowing along the inner surface; and a combustion chamber 330 having a cylindrical structure that is longer than the turbulence chamber 320 with a smaller cross-sectional area, in which one end is connected to the center portion of the turbulence chamber 320, and a mixture of the metal powder and the steam fed through a connection unit connected with the turbulence chamber 320 spirally flows along the inner surface and proceeds toward the other end.

In addition, the turbulence chamber 300 may include: a guide projection unit 321 having an inner center projected toward the combustion chamber 330, for guiding proceed of flow toward the combustion chamber 330.

In addition, the metal powder feeder 100 may include: a powder tank 110 for storing the metal powder, having an outlet for exhausting the metal powder and a carriage gas inlet for taking in carriage gas, respectively formed at an upper portion and a lower portion; and a carriage gas feeder 120 for floating some of the metal powder stored and stacked in the powder tank 110 toward the outlet side by feeding the carriage gas into the powder tank 110 through the carriage gas inlet, and feeding the metal powder to the combustion chamber 300.

In addition, the carrier gas feeder 120 may include: a gas tank 121 for storing the carriage gas; a pressure transducer 122 installed on a gas feed tube formed between the gas tank 121 and the powder tank 110, for measuring pneumatic pressure; an electronic scale 123 for measuring an amount of the metal powder fed into the combustion chamber 300 by measuring weight of the powder tank 110; and a powder feed controller 124 for controlling the amount of the metal powder fed into the combustion chamber 300 with respect to supply of the carriage gas based on data measured using the pressure transducer 122 and the electronic scale 123.

In addition, the compact metal powder combustion apparatus may further comprise: a purge gas feeder 600 having a feed terminal connected to the powder feed tube formed between the powder tank 110 and the combustion chamber 300 so as to feed purge gas into the combustion chamber 300 in place of the metal powder.

In addition, the steam feeder 200 may include: a steam generator 210 for receiving electric power and water and generating super-heated steam; and a steam feed controller 220 for controlling an amount of the steam fed into the combustion chamber 300 through a bypath 221 branched from a steam feed tube formed between the steam generator 210 and the combustion chamber 300.

In addition, the compact metal powder combustion apparatus may further comprise: a steam cooler 230 for cooling and exhausting the super-heated steam passing through the bypath 221 from the steam feed tube, through heat exchange with coolant.

In addition, the water plasma igniter 400 injects the water plasma, ionized hydrogen and oxygen plasma of 1,000oC or higher using the steam as a supply gas, into the combustion chamber 300.

In addition, the compact metal powder combustion apparatus may further comprise: a precipitator 500 installed at a combustion gas exhausting terminal for exhausting gas in the combustion chamber 300, for precipitating metal powder slug generated in a combustion process so that the slug may not be exhausted outside.

In addition, according to another aspect of the present invention, there is provided a metal powder combustion method using water plasma, the method comprising: a metal powder feeding step of feeding a right amount of metal powder and steam of 200 to 400° C. into a combustion chamber 300; a mix and flow step of mixing the metal powder and the steam inside the combustion chamber 300 by swirl flow; an ignition step of igniting the metal powder and the steam in the combustion chamber 300 using the water plasma, in which the metal powder is a fuel, and the steam is an oxidizer; and an ignition maintaining step of maintaining injection of the water plasma for a predetermined time period, as long as combustion of the metal powder is continued, although ignition of the metal powder succeeded.

Here, in the metal powder feeding step, the metal powder and/or the steam may be fed into the combustion chamber 300 in the tangential direction through mutually independent paths.

In addition, in the metal powder feeding step, the metal powder may be preheated by an energy recuperation system or a regenerative heat exchanger and then fed into the combustion chamber 300.

In addition, the mix and flow step may include: a premixing step of mixing the metal powder and the steam fed into the combustion chamber 300 in the tangential direction, by circulating the metal powder and the steam along the inner surface inside a disk-shaped mixing space unit of the combustion chamber 300 by swirl flow; and a spiral flow step of feeding a mixture of the metal powder and the steam generated in the premixing step into a separate cylindrical space unit inside the combustion chamber 300, and proceeding the mixture to one side by spiral flow over a further extended staying time.

In addition, in the ignition step, the steam may be ionized into hydrogen and oxygen plasma of 1,000° C. or higher using the steam as a supply gas and injected into the combustion chamber 300.

In addition, the metal powder combustion method may further include: a combustion maintaining step of feeding only the metal powder and the steam into the combustion chamber 300 and maintaining combustion of the metal powder while injection of the water plasma is stopped, after the ignition maintaining step.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a table showing reaction formulas and reaction heats of hydrocarbon fuel, aluminum, and magnesium.

FIG. 2 is a mimetic view showing the process of igniting aluminum metal particles.

FIG. 3 is a flowchart illustrating the process of igniting aluminum metal particles.

FIG. 4 is a conceptual view showing a compact metal powder combustion apparatus using water plasma according to a first embodiment of the present invention.

FIG. 5 is a perspective view showing a combustion chamber.

FIG. 6 is a front view showing the combustion chamber of FIG. 5.

FIG. 7 is a left-side view showing the combustion chamber of FIG. 5.

FIG. 8 is a picture showing a prototype of a compact metal powder combustion apparatus actually manufactured according to a first embodiment of the present invention.

FIG. 9 is a graph showing the amount of metal powder supplied with respect to the pressure of supplied carrier gas, measured at a metal powder feeder.

FIG. 10 is a graph showing the amount of steam supplied with respect to the. pressure inside a steam generator, measured at a steam feeder.

FIG. 11 is a graph showing temperature gradients at the nozzle of a water plasma igniter.

FIG. 12 is a graph showing an example of measuring intensity of light using a photo multiplier tube with respect to ignition and combustion of aluminum powder.

FIG. 13 is a picture showing a combustor when an igniter is in operation before metal powder is supplied.

FIG. 14 is a picture showing a combustor burning metal powder after the metal powder is supplied.

FIG. 15 is a picture showing a combustor further actively burning the metal powder compared with the combustor shown in FIG. 14 by adjusting the amount of supplied steam.

FIG. 16 is a picture showing a combustor when operation of the igniter is stopped.

FIG. 17 is a picture showing a combustor when flames are extinguished by stopping supply of metal powder.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The present invention relates to a metal powder ignition apparatus, a metal powder ignition method, a compact metal powder combustion apparatus, and a metal powder combustion method using water plasma. The present invention relates to a technique for implementing a compact clean combustion apparatus for igniting metal powder using water plasma while feeding a right amount of metal powder and steam into the combustion chamber.

According to an embodiment of the present invention, thermal energy of high efficiency can be generated using only metal and steam, in which the metal and the steam are used as a fuel and an oxidizer, and the water is used as a supply gas of the water plasma. Therefore, it is possible to implement an environment-friendly thermal energy acquiring apparatus which does not exhaust ignition contaminants and polluted gas at all.

The preferred embodiments of the present invention will be hereafter described in detail, with reference to the accompanying drawings.

FIG. 4 is a conceptual view showing a compact metal powder combustion apparatus using water plasma according to a first embodiment of the present invention.

Referring to FIG. 4, the compact metal powder combustion apparatus using water plasma according to a first embodiment of the present invention includes a metal powder feeder 100, a steam feeder 200, a combustion chamber 300, a water plasma igniter 400, a precipitator 500, and a purge gas feeder 600.

The metal powder feeder 100 is an apparatus for feeding a right amount of metal powder into the combustion chamber 300. The metal powder feeder 100 includes a powder tank 110 for storing and stacking the metal powder and a carrier gas feeder 120 for feeding and controlling carriage gas in order to form a pressure difference or fluid flow to carry the metal powder to the combustion chamber 300.

The powder tank 110 provides a storage space capable of accommodating a predetermined height or amount of metal powder inside, in which a carriage gas inlet (symbol is not shown) for taking in the carriage gas is formed at a lower portion, and an outlet (symbol is not shown) for exhausting the metal powder together with the carriage gas to the combustion chamber 300 is formed at an upper portion.

As shown in the table of FIG. 1, the metal powder contains a high-energy metal material as its component, such as aluminum or magnesium that is proved to have a high reaction heat compared with hydrocarbon fuel.

The carriage gas feeder 120 floats some of the metal powder stored and stacked in the powder tank 110 toward the outlet side by feeding the carriage gas into the powder tank 110 through the carriage gas inlet, thereby feeding the metal powder into the combustion chamber 300.

An inert gas such as argon (Ar) or the like is preferably used as the carriage gas so as to prevent oxidation or the like of the metal powder, and the carriage gas feeder 120 includes a gas tank 121, a pressure transducer 122, an electronic scale 123, and a powder feed controller 124.

The carriage gas stored in the gas tank 121 in a compressed state is fed into the powder tank 110 through a gas feed tube (symbol is not shown) formed between the gas tank 121 and the storage gas inlet of the powder tank 110.

The pressure transducer 122 is installed to measure pneumatic pressure inside the gas feed tube, and the electronic scale 123 is installed at a lower portion of the powder tank 110 to sense changes the mass of the metal powder, i.e., the amount of metal powder fed into the combustion chamber 300, by measuring weight of the powder tank 110.

The powder feed controller 124 collects data (DAQ, Data Acquisition) measured by the pressure transducer 122 and the electronic scale 123 and controls the amount of the metal powder fed into the combustion chamber 300 according to the amount of supplied carriage gas based on the collected data.

It is possible to flexikly and accurately control increase or decrease of the amount of metal powder exhausted toward the combustion chamber 300 through the outlet of the powder tank 110, by controlling increase and decrease of the amount of the supplied carriage gas by the powder feed controller 124 while confirming the amount of supplied carriage gas and metal powder using the pressure transducer 122 and the electronic scale 123 in real-time.

The metal powder exhausted through the outlet of the powder tank 110 is fed into the combustion chamber 300 through the powder feed tube (symbol is not shown) formed between the powder tank 110 and the combustion chamber 300.

A feed terminal of the purge gas feeder 600 for feeding purge gas is connected to the powder feed tube, and the metal powder is fed into the combustion chamber 300 through the powder feed tube while the metal powder is ignited and combusted, and the purge gas is fed into the combustion chamber 300 in place of the metal powder when flames are extinguished and the metal powder is not combusted.

The steam feeder 200 is an apparatus for generating super-heated steam of 200 to 400° C. and feeding the steam into the combustion chamber 300, and the steam feeder 200 includes a steam generator 210, a steam feed controller 220, and a steam cooler 230.

The steam generator 210 receives electric power and water and generates super-heated steam. If specifications of the water plasma igniter 400 are fixed, ignition and combustion can be further stably performed as the temperature of the steam fed into the combustion chamber 300 is higher. Therefore, it is preferable to heat the steam up to 200° C. or higher, but not to exceed 400° C. considering safety issues raised by the super-heated steam fed through a tube and energy efficiency of using the electric power.

The super-heated steam generated by the steam generator 210 is fed into the combustion chamber 300 through a steam feed tube (symbol is not shown) formed between the steam generator 210 and the combustion chamber 300.

The steam feed controller 220 controls increase and decrease of the amount of the steam fed into the combustion chamber 300 using a control valve installed on the steam feed tube and the bypath 221 branched from the steam feed tube.

The steam cooler 230 is an apparatus for cooling and exhausting super-heated steam that is not fed into the combustion chamber 300 and passing through the bypath 221 from the steam feed tube, through heat exchange with coolant. The steam cooler 230 can cool down the steam through the heat exchange while passing the steam through a coolant tank or the like and exhaust or discharge the steam to a predetermined place outside the combustion apparatus using a pump.

FIGS. 5, 6 and 7 respectively show a perspective view, a front view and a left-side view of the combustion chamber.

Referring to FIGS. 4 to 7, the combustion chamber 300 is an apparatus for receiving the metal powder and the steam from the metal powder feeder 100 and the steam feeder 200 and allowing the metal powder and the steam to be combusted by the water plasma igniter 400. The combustion chamber 300 includes a tangential feed tube 310, turbulence chamber 320, and a combustion chamber 330.

The tangential feed tube 310 is a part for receiving the metal powder and the steam from the metal powder feeder 100 and the steam feeder 200, in which a connection unit (hereinafter, referred to as a feed terminal) connected with the combustion chamber 300 is connected to the outer circumference of the combustion chamber 300 in the tangential direction.

Owing to the structure of the tangential feed tube 310 connected to the outer circumference of the combustion chamber 300 in the tangential direction, the metal powder and the steam are fed into the combustion chamber 300 in the tangential direction.

If feed terminals of a first tangential feed tube 311 for feeding the metal powder and a second tangential feed tube 312 for feeding the steam are arranged on the outer circumference of the combustion chamber 300 at predetermined intervals, the metal powder and the steam fed into the combustion chamber 300 in the tangential direction swirl-flows in the same moving path along the inner surface of the combustion chamber 300 and may be evenly mixed with each other.

The turbulence chamber 320 provides a narrow disk-shaped mixing space unit in which the metal powder and the steam fed through the first and second tangential feed tubes 311 and 312 are mixed while swirl-flowing along the inner surface, and a strong turbulence of the mixed metal powder and steam (hereinafter, referred to as a mixture) may be formed inside the turbulence chamber 320 owing to the structure arranging the tangential tube 310 as described above.

The combustion chamber 330 has a cylindrical structure that is longer than the turbulence chamber 320 with a smaller cross-sectional area, and one end of the combustion chamber 300 is connected to the center of the turbulence chamber 320. The mixture of the metal powder and the steam fed through the connection unit connected with the turbulence chamber 320 spirally flows along the inner surface and proceeds toward the other end of the combustion chamber 330.

Inside the turbulence chamber 320, a guide projection unit 321 having a slanted or curved profile shape so as to gradually reduce the width thereof toward the combustion chamber 330 and projecting toward the combustion chamber 330 is formed at the center, and thus the direction of the flow mainly proceeding in the tangential direction inside the turbulence chamber 320 is guided toward the combustion chamber 330 as the metal powder, the carriage gas, and the steam are fed in.

The mixture inside the turbulence chamber 320 gradually changes from a swirl flow form in which the mixture repeatedly circulates along a circular path to a spiral flow form and proceeds toward the combustion chamber 330, and the mixture deflectedly fed into the combustion chamber 330 proceeds continuously implementing the spiral flow along the inner surface of the combustion chamber 330.

As the time of the metal powder and the steam staying in the combustion chamber 300 is extended, further stable ignition and combustion may be implemented by improving the contact among the fuel, oxidizer, and ignition heat. However, conventionally, the time staying in the combustion chamber is extended long by simply forming the combustion chamber to be lengthy, and thus it is difficult to practically utilize the combustion apparatus in industry due to the problems of preheating and loss of heat in the combustion chamber.

According to the structure of the combustion chamber 300, the metal powder may be prevented from being clotted and evenly distributed and mixed with the steam owing to the high-speed swirl flow and spiral flow of the mixture. Furthermore, uniform heat flux may be implemented across the combustion chamber 300.

In addition, the time of the mixture staying in the combustion chamber 300 may be increased, and the metal powder is combusted to be further close to complete combustion by increasing the speed of combustion and flame propagation. Therefore, it is possible to output high power and implement a compact combustion chamber smaller than conventional ones.

The water plasma igniter 400 is an apparatus for igniting the metal powder and the steam fed into the combustion chamber 300 using the water plasma. The water plasma igniter 400 ignites and burns the metal powder by injecting water plasma of 1,000° C. or higher into the mixture of the metal powder and the steam functioning as an oxidizer for burning the metal powder.

The state of a material changes from solid to liquid and then from liquid to gas as the temperature increases. If the gas is continuously heated to reach several thousands degrees (° C.), molecules of the gas are dissociated into atoms, and the atoms are ionized into ions having electrons and positive charges.

The gas separated into electrons and ions at a high temperature like this, which is neutralized since the number of negative charges is almost the same as that of positive charges and still has a considerably high degree of electrolytic dissociation compared with that of neutral atoms, is called as plasma.

Generally, the plasma is generated through an electron heating process in which electrons obtain energy from electric fields and an ionization process of removing electrons of neutral particles, and a water plasma apparatus which ionizes steam into hydrogen and oxygen plasma of 1,000° C. or higher using the steam as a supply gas may be applied as the water plasma igniter 400, in which the hydrogen and oxygen plasma may ignite and burn the metal powder.

The water plasma igniter 400 may generate high temperature plasma of 1,000° C. or higher using the steam as a supply gas as described above. If a plasma injection terminal can be installed inside the combustion chamber 300, the water plasma igniter 400 is not limited to a specific structure and form including publicized water plasma apparatuses and follows a basic structure of a water plasma apparatus capable of generating high temperature plasma using the steam as a supply gas. Therefore, details thereof will not be described.

It is preferable to apply a different temperature and a different injection amount to the water plasma depending on ingredients, particle size, and the like of the metal powder. For example, if the major ingredient of the metal powder is aluminum, a specification capable of generating plasma of 2,345K or higher, which is the melting temperature of an aluminum oxide film, is applied.

The water plasma is injected toward the center of the combustion chamber 300 positioned at the core of the swirl flow, in the proceeding direction of the metal powder and the steam, i.e., injected toward the combustion chamber 330 from the turbulence chamber 320, and ignites and burns the metal powder in the combustion chamber 330.

The precipitator 500 is installed at a combustion gas exhausting terminal for exhausting the gas in the combustion chamber 300 and precipitates metal powder slug generated in the combustion process so that the slug may not be exhausted outside. If the precipitator 500 includes an electrostatic precipitator and the like and may separate, collect, and remove dusts or the like floating in the combustion gas, it is not limited to a specific structure and form including existing publicized techniques.

Next, a metal powder combustion method of a compact metal powder combustion apparatus using water plasma according to a first embodiment of the present invention (hereinafter, referred to as a metal powder ‘combustion method using water plasma’) will be described.

The metal powder combustion method using water plasma according to a first embodiment of the present invention may be accomplished by sequentially performing a metal powder feeding step, a mix and flow step, an ignition step, an ignition maintaining step, and a combustion maintaining step.

In the metal powder feeding step, a right amount (an amount predetermined to be appropriate for combustion) of metal powder and steam of 200 to 400° C. is fed into the combustion chamber 300. The metal powder and the steam are fed into the combustion chamber 300 in the tangential direction through mutually independent paths corresponding to the metal powder feeder 100 and the first tangential feed tube 311, and the steam feeder 200 and the second tangential feed tube 312.

A premixing step and a spiral flow step are sequentially performed in the mix and flow step. The metal powder and the steam are mixed inside the combustion chamber 300 by swirl flow, and the mixture thereof spirally flows and proceeds to one side of the combustion chamber 300.

In the premixing step, the metal powder and the steam fed into the combustion chamber 300 in the tangential direction are mixed while circulating along the inner surface inside the turbulence chamber 320 of the combustion chamber by swirl flow, and the metal powder and the steam are guided to flow toward the combustion chamber 330 of the combustion chamber 300 where combustion of the metal powder is mainly performed.

In the spiral flow step, a mixture of the metal powder and the steam generated in the premixing step is fed into the combustion chamber 330 of a cylindrical shape formed to be separated from the turbulence chamber 320, and the mixture proceeds to one side by spiral flow while staying in the combustion chamber 330 of a limited length for a further extended period of time.

In the ignition step, the metal powder and the steam fed into the combustion chamber 300 are ignited using the water plasma of high temperature injected from the water plasma igniter 400. The water plasma igniter 400 ionizes the steam into hydrogen and oxygen plasma of 1,000° C. or higher using the steam as a supply gas and injects the plasma into the combustion chamber 300.

The ignition step is a process of igniting the metal powder using the water plasma, and the water plasma igniter 400 may start its operation in the ignition step, or the metal powder may be ignited after performing the mix and flow step while the water plasma igniter 400 is in operation, before the metal powder feeding step is performed.

In order to accelerate ignition in the ignition step, the metal powder feeding step may be performed after the preheating step where the metal powder is preheated to a temperature higher than ambient temperature.

In preheating the metal powder in the metal powder preheating step, although a separate electric power or heat energy source may be used, the metal powder may be preheated by an energy recuperation system or a regenerative heat exchanger using, as an energy source, the energy consumed when the compact metal powder combustion apparatus according to a first embodiment operates, such as thermal energy of super heated steam separated and exhausted from the steam feeder 200 through the bypath 221.

If the metal powder is aluminum particles, the process requiring the longest time in the ignition step is the process of removing the oxide film, and the aluminum particles should be heated up to 2,345K in order to remove the aluminum oxide film. If the metal powder is preheated, the time required for arriving at the melting temperature may be saved.

If the operation of the water plasma igniter 400 is immediately stopped after the metal powder is ignited in the ignition step, although supply of the metal powder and the steam into the combustion chamber 300 is continued, the state of igniting and burning the metal powder is not maintained, and the flames are extinguished.

In the ignition maintaining step, therefore, the injection of the water plasma is maintained for a predetermined time period if supply of the metal powder and the steam into the combustion chamber 300 is continued, although the ignition of the metal powder succeeded.

In the combustion maintaining step, only the metal powder and the steam are fed into the combustion chamber 300 while injection of the water plasma is stopped by stopping operation of the water plasma igniter 400, and combustion of the metal powder is maintained.

Next, a prototype of a metal powder ignition apparatus using water plasma and a compact combustion apparatus according to an embodiment of the present invention configured as described above is actually manufactured, and the process and results of an experiment implementing and confirming ignition and combustion using only the metal powder and the steam will be described below.

FIG. 8 is a picture showing a prototype of a compact metal powder combustion apparatus, which is a compact combustion apparatus using water plasma actually manufactured according to a first embodiment of the present invention.

Referring to FIG. 8, the metal powder feeder 100, the steam feeder 200, the combustion chamber 300, the water plasma igniter 400, and the precipitator 500 are configured in the prototype. In the atmospheric environment, metal powder of several micro meters is used as a fuel, argon is used as a carriage gas, and steam is used as an oxidizer. The combustion phenomenon is observed after the metal powder is ignited using super-heated water plasma.

FIG. 9 is a graph showing the amount of metal powder supplied with respect to the pressure of supplied carrier gas, measured at a metal powder feeder 100.

While supplying argon carriage gas toward the powder tank 110 where the metal powder is stored, the metal powder is carried and fed into the combustion chamber 300 in the form of a fluidized bed in which the metal powder is evenly distributed and mixed on the carriage gas, and the metal powder is continuously measured by the electronic scale 123 in this process.

Referring to FIG. 9, it can be confirmed that the mass of the metal powder in the powder tank 110 linearly decreases at a certain rate, and a mass flow rate of 32 g/min (0.54 g/sec) is measured in average.

FIG. 10 is a graph showing the amount of steam supplied with respect to the pressure inside a steam generator 210, measured at the steam feeder 200.

Water of room temperature and electric power are supplied to the steam generator 200, and steam heated to be high temperature vapor of about 370 to 400° C. using an electric heater is fed into the combustion chamber 300. Then, surplus of the steam exceeding a predetermined amount is condensed by the steam cooler 230 and exhausted through the bypath 221.

The steam is fed into the combustion chamber 300 in the spray form using an injector in order to uniformly mix the steam with the metal powder, and geometric shape variables of the injector are designed comprehensively considering an axial to tangential direction momentum ratio, an injection angle, an amount of flow, supplied pressure, and the like.

Referring to FIG. 10, when the temperature and pressure in the steam generator 210 are maintained in a stable state of about 370 to 385° C. and 3.5 to 4.5 bar, a mass flow rate of 49.4 g/min is measured in average.

FIG. 11 is a graph showing temperature gradients at the nozzle of the water plasma igniter 400.

A water plasma torch is applied as the water plasma igniter 400, and water plasma is injected into the combustion chamber 300 through a nozzle formed at one end of the water plasma torch.

Referring to FIG. 11, it is confirmed that a temperature field of 1,000° C. or higher and a temperature field of 3,000° C. or higher are formed respectively within a distance of 50 mm and 10 mm from the nozzle terminal of the water plasma igniter 400, and the injected water plasma has a maximum temperature of 4,000° C. or higher. Accordingly, it is confirmed that the water plasma is appropriate for being applied as an ignition energy source for igniting aluminum or magnesium (melting point is 650° C.)

FIG. 12 is a graph showing an example of measuring intensity of light using a photo multiplier tube with respect to ignition and combustion of aluminum powder.

There are contact and none-contact type measurement methods in measuring temperature to confirm the state of ignition and combustion. In the case of the contact type measurement method, a measured temperature is unreliable due to adhesiveness of the metal powder and excessive heat transfer of a measurement device, and thus intensity of light is measured using a photo multiplier tube (PMT) in the experiment, and a photodiode or a charge coupled device (CCD) may be used other than the PMT.

In the graph shown in FIG. 12, there is a section where intensity of light abruptly increases, and it may be determined that ignition starts at this point. Accordingly, a time interval between the time point where the water plasma is injected and the time point where the light of intensity abruptly increases may be determined as an ignition delay time.

FIG. 13 is a picture showing a combustor when an igniter is in operation before metal powder is supplied, and FIG. is a picture showing a combustor burning the metal powder after the metal powder is supplied. FIG. 15 is a picture showing a combustor further actively burning the metal powder compared with the combustor shown in FIG. 14 by adjusting the amount of supplied steam, FIG. 16 is a picture showing a combustor when operation of the igniter is stopped, and FIG. 17 is a picture showing a combustor when flames are extinguished by stopping supply of metal powder.

The purge gas and the super-heated steam (oxidizer) are previously fed into the combustion chamber 300 by the purge gas feeder 600 and the steam feeder 200 and then preheated. The metal powder is fed by the metal powder feeder 100 while the water plasma igniter 400 is in operation. The metal powder has a particle size of 74 μm, and magnesium powder containing a small amount of silicon, manganese and the like and having purity of 98.5% is used as a raw material of the metal powder.

A compact combustion chamber having a length of 220 mm in the axial direction is designed based on the structure of the combustion chamber 300 which supplies the metal powder and the steam in the tangential direction, premixes the metal powder and the steam by swirl flow, and proceeds the mixture of the metal powder and the steam toward one side by spiral flow.

It is confirmed that ignition is unsuccessful as shown in FIG. 13 before the metal powder is fed while the water plasma igniter 400 is in operation, and ignition is succeeded as shown in FIG. 14 after the metal powder is supplied. It is possible to implement further active ignition as shown in FIG. 15 by adjusting the ratio of the metal powder and the steam supplied.

It is confirmed that although the operation of the water plasma igniter 400 is stopped, combustion is continued as shown in FIG. 16 by only feeding the metal powder (fuel) and the steam (oxidizer), and flames are extinguished as shown in FIG. 20 by stopping supply of the metal powder.

Combustion is continued as shown in FIG. 16 when the amount of the supplied magnesium powder is about 32 g/min (0.54 s/sec) as shown in FIG. 9. If it is assumed that all the magnesium powder reacts to the oxidizer, it may be determined that the combustion is continued in a condition where the fuel is scarce as low as a stoichiometric ratio of 0.49. If the stoichiometric ratio is converted into a number density per unit volume, it is about 200 g/m3, which is a remarkably high number density compared with a number density of 30 g/m³ generally known as a lower explosive limit of a metal.

According to the present invention configured as described above, it is implemented a compact clean combustion apparatus for igniting metal powder using water plasma while feeding only a right amount of the metal powder and the steam into the combustion chamber, and thus metal fuels can be stably used (industrialized and commercialized) as an environment-friendly alternative high-power energy source that is free from environmental pollution.

Accordingly, unlike the cases of using existing carbon fuels (coal, petroleum and the like) or hydrocarbon fuels (methane gas, propane gas and the like), the combustion apparatus may be independently applied or additionally applied in combination with an existing heating unit or the like, as an environment-friendly thermal energy acquisition apparatus that does not exhaust contaminant or pollutant gas.

In addition, since the water plasma apparatus is applied as a source of ignition, metal powder may be stably ignited by high-temperature plasma particles supplied by the water plasma apparatus. Furthermore, since oxygen and hydrogen ions of water plasma are supplied, the amount of steam supplied as an oxidizer may be reduced, and pollution caused by plasma feeding gas (e.g., Ar or the like) can be prevented fundamentally.

In addition, if the water plasma apparatus is applied, relatively low voltage is used compared with existing arc plasma apparatuses. Since steam (water) is used as a feeding gas, safe and environment-friendly ignition energy may be provided at a low cost without worrying about generation of toxic gases.

In addition, if aluminum powder is used as the metal powder, alumina (Al₂O₃), which is a product generated after combustion, is renewable through reprocessing, and hydrogen (H₂) may be used as an energy source through a fuel cell.

For example, the energy generated through combustion reaction of the aluminum metal powder may be used as energy for driving a turbine, and hydrogen which is a product of the combustion may be used as an energy source of a fuel cell through reprocessing. If seawater is used as an oxidizer, the present invention may be extendedly applied to a propulsion engine or the like of a military super-cavitating torpedo.

In addition, the present invention may be applied to process industrial wastes of aluminum or applied to combustion of aluminum as a method of producing hydrogen or ceramic alumina powder.

While the present invention has been described with reference to the particular illustrative embodiments, it is not to be restricted by the embodiments but only by the appended claims. It is to be appreciated that those skilled in the art can change or modify the embodiments without departing from the scope and spirit of the present invention. 

1. A metal powder ignition apparatus using water plasma, the apparatus for igniting and burning metal powder by injecting the water plasma to a mixture of the metal powder and steam functioning as an oxidizer for burning the metal powder.
 2. The apparatus according to claim 1, wherein the metal powder is manufactured using aluminum or magnesium, and the water plasma is high-temperature plasma of 1,000° C. or higher generated by ionizing the steam.
 3. A metal powder ignition method using water plasma, the method for igniting metal powder in a combustion chamber using the water plasma while feeding only a right amount of the metal powder and the steam into the combustion chamber.
 4. The method according to claim 3, wherein the metal powder and the steam stay inside a space unit of a limited length in the combustion chamber for a further extended period of time and proceed toward one side by swirl flow, and the water plasma is injected toward a center of the combustion chamber positioned at a core of the swirl flow, in a proceeding direction of the metal powder and the steam.
 5. A compact metal powder combustion apparatus using water plasma, the apparatus comprising: a combustion chamber; a metal powder feeder for feeding the metal powder into the combustion chamber; a steam feeder for generating steam of 200 to 400° C. and feeding the steam into the combustion chamber; and a water plasma igniter for igniting the metal powder and the steam fed into the combustion chamber, using the water plasma.
 6. The apparatus according to claim 5, wherein the combustion chamber includes: a tangential feed tube having a feed terminal connected to an outer circumference of the combustion chamber in a tangential direction, for generating swirl flow by feeding the metal powder and/or the steam into the combustion chamber in the tangential direction.
 7. The apparatus according to claim 6, wherein the combustion chamber includes: a turbulence chamber having feed terminals of a first tangential feed tube for feeding the metal powder and a second tangential feed tube for feeding the water, arranged on the outer circumference at predetermined intervals, and forming a narrow disk-shaped mixing space unit in which the metal powder and the steam fed through the first and second tangential feed tubes 311 and 312 are mixed while swirl-flowing along an inner surface; and a combustion chamber having a cylindrical structure that is longer than the turbulence chamber with a smaller cross-sectional area, in which one end is connected to a center portion of the turbulence chamber, and a mixture of the metal powder and the steam fed through a connection unit connected with the turbulence chamber spirally flows along the inner surface and proceeds toward the other end.
 8. The apparatus according to claim 7, wherein the turbulence chamber includes: a guide projection unit having an inner center projected toward the combustion chamber, for guiding proceed of flow toward the combustion chamber.
 9. The apparatus according to claim 5, wherein the metal powder feeder includes: a powder tank for storing the metal powder, having an outlet for exhausting the metal powder and a carriage gas inlet for taking in carriage gas, respectively formed at an upper portion and a lower portion; and a carriage gas feeder for floating some of the metal powder stored and stacked in the powder tank toward the outlet side by feeding the carriage gas into the powder tank 110 through the carriage gas inlet, and feeding the metal powder to the combustion chamber.
 10. The apparatus according to claim 9, wherein the carrier gas feeder includes: a gas tank for storing the carriage gas; a pressure transducer installed on a gas feed tube formed between the gas tank and the powder tank, for measuring pneumatic pressure; an electronic scale for measuring an amount of the metal powder fed into the combustion chamber by measuring weight of the powder tank; and a powder feed controller for controlling the amount of the metal powder fed into the combustion chamber with respect to supply of the carriage gas based on data measured using the pressure transducer and the electronic scale.
 11. The apparatus according to claim 9, further comprising: a purge gas feeder having a feed terminal connected to the powder feed tube formed between the powder tank and the combustion chamber so as to feed purge gas into the combustion chamber in place of the metal powder.
 12. The apparatus according to claim 5, wherein the steam feeder includes: a steam generator for receiving electric power and water and generating super-heated steam; and a steam feed controller for controlling an amount of the steam fed into the combustion chamber through a bypath branched from a steam feed tube formed between the steam generator and the combustion chamber.
 13. The apparatus according to claim 12, further comprising: a steam cooler for cooling and exhausting the super-heated steam passing through the bypath from the steam feed tube, through heat exchange with coolant.
 14. The apparatus according to claim 5, wherein the water plasma igniter injects the water plasma, ionized hydrogen and oxygen plasma of 1,000° C. or higher using the steam as a supply gas, into the combustion chamber.
 15. The apparatus according to claim 5, further comprising: a precipitator installed at a combustion gas exhausting terminal for exhausting gas in the combustion chamber, for precipitating metal powder slug generated in a combustion process so that the slug may not be exhausted outside.
 16. A metal powder combustion method using water plasma, the method comprising: a metal powder feeding step of feeding a right amount of metal powder and steam of 200 to 400° C. into a combustion chamber; a mix and flow step of mixing the metal powder and the steam inside the combustion chamber by swirl flow; an ignition step of igniting the metal powder and the steam in the combustion chamber using the water plasma, wherein the metal powder is a fuel, and the steam is an oxidizer; and an ignition maintaining step an ignition maintaining step of maintaining injection of the water plasma for a predetermined time period, as long as combustion of the metal powder is continued, although ignition of the metal powder succeeded.
 17. The method according to claim 16, wherein in the metal powder feeding step, the metal powder and/or the steam is fed into the combustion chamber in a tangential direction through mutually independent paths.
 18. The method according to claim 16, wherein in the metal powder feeding step, the metal powder is preheated by an energy recuperation system or a regenerative heat exchanger and then fed into the combustion chamber.
 19. The method according to claim 16, wherein the mix and flow step includes: a premixing step of mixing the metal powder and the steam fed into the combustion chamber in a tangential direction, by circulating the metal powder and the steam along an inner surface inside a disk-shaped mixing space unit of the combustion chamber 300 by swirl flow; and a spiral flow step of feeding a mixture of the metal powder and the steam generated in the premixing step into a separate cylindrical space unit inside the combustion chamber, and proceeding the mixture to one side by spiral flow over a further extended staying time.
 20. The method according to claim 16, wherein in the ignition step, the steam is ionized into hydrogen and oxygen plasma of 1,000° C. or higher using the steam as a supply gas and injected into the combustion chamber.
 21. The method according to claim 16, further comprising: a combustion maintaining step of feeding only the metal powder and the steam into the combustion chamber and maintaining combustion of the metal powder while injection of the water plasma is stopped, after the ignition maintaining step. 